We propose to further develop our optimal feedback control theory of motor coordination, and utilize its potential to explain known phenomena and as well as novel experimental results on goal-directed arm movements in 2D and 3D. We will use the theory to shed new light on several important issues in sensorimotor control: regularities in kinematics and muscle activations, task-specific impedance and responses to perturbations, origins and structure of motor variability, and eye-hand coordination patterns. In addition to basic research, the project involves a substantial bio-engineering component with direct applications to health. We will construct detailed musculoskeletal models of the human arm and develop hierarchical control algorithms capable of making the model arm accomplish behavioral goals in real time. Such algorithms can then be used to control functional electric stimulators and robotic prostheses, and thereby restore motor function and improve the quality of life of disabled patients. PUBLIC HEALTH RELEVANCE: We will develop a general mathematical theory of how the brain controls arm movements. Better theoretical understanding of motor function can facilitate the design of new treatments for movement disorders. We will also develop automatic control algorithms that can use signals extracted from the brain to make a prosthetic arm accomplish desired movement goals.